Plack::Builder gives you a quick domain specific language (DSL) to wrap your application with Plack::Middleware subclasses. The middleware you're trying to use should use Plack::Middleware as a base class to use this DSL, inspired by Rack::Builder.

Whenever you call enable on any middleware, the middleware app is pushed to the stack inside the builder, and then reversed when it actually creates a wrapped application handler. "Plack::Middleware::" is added as a prefix by default. So: